If you have a GMMK Pro I HIGHLY recommend the AVX Works FR4 plate. The look and Durock fitment was worth the $25 alone to me. It sounds really nice too! :
POM vs FR4 vs CF vs ALU vs Brass vs Copper vs Silver Mirror | Plate Material Comparison - YouTube
Plate Material Sound Comparison - Alu vs Brass vs Steel vs Carbon Fiber vs Polycarbonate - YouTube
Alu vs Brass vs FR4 vs POM vs Polycarbonate Plate (Linear) - YouTube
QK65 Keyboard | All 4 Plates Comparison Typing Test | QwertyKeys - YouTube
FR4 PCB vs. Aluminum PCB vs. Copper PCB vs. Ceramic PCB
Percent Studio Luna 75 Diy Mechanical Keyboard Pc Fr4 Positioning Keyboard Plate - Buy Keyboard Plate,Positioning Board Plate,Custom Keyboard Kit Product on Alibaba.com
FR4 on KBD67 Lite vs PC Plate Sound Test - Durock POM T1's (Sunflowers) - YouTube
KBD67 Lite w/ Tecsee Purple Panda FR4 vs PC Plate - For sound reference : r/MechanicalKeyboards
The GMMK Pro FR4 plate by AVX Works : r/MechanicalKeyboards
KBD67 Lite R3 Plate Comparison: PC vs FR4 vs POM - YouTube
Has anybode ever used a FR4 "plate" ?
The tale of the flexing plates.
FR4 60% PLATE, Computers & Tech, Parts & Accessories, Computer Keyboard on Carousell
QK65 R1 Extra Plates and PCBs – Rebult Keyboards
Buy Keychron Q1 FR4 Plate [Q1P-FR4] | PC Case Gear Australia